1. Field of the Invention
This invention relates to a method for manufacturing circuit devices, and more particularly to a method for manufacturing circuit devices including a resin sealing step that can prevent a planar body from being deformed inside a mold cavity.
2. Description of the Related Art
Referring to FIGS. 13(A)–13(C), a description will be given of a conventional method for manufacturing circuit devices. FIG. 13(A) is a sectional view of the step of performing transfer molding, FIG. 13(B) is a plan view of a conductive foil 110, and FIG. 13(C) is a sectional view seen when molding is performed.
Referring to FIGS. 13(A) and 13(B), a brief description will be given of steps prior to performing a molding operation. First, a conductive pattern 121A, 121B and/or 121C is formed by forming a separation groove 111 in a conductive foil 110. The conductive pattern 121 forms a block 112 by arranging mounting portions, each of which forms a circuit device, in a matrix form. A semiconductor element 122A and a chip resistor 122B are then fixed to a conductive pattern 121A of each mounting portion. Further, the semiconductor element 122A is electrically connected through a fine metal wire 125A to a conductive pattern 121B. Each block 112 is then sealed with an insulating resin 120 by use of a cavity. Through these steps, a circuit element 122 of each block 112 is sealed, and the separation groove 111 is also filled with the insulating resin 120.
Referring to FIG. 13(C), a description will be given of a sealing step that uses a mold 128A, 128B. The mold 128A, 128B used to perform resin sealing for each block 112 consists of a lower mold 128A and an upper mold 128B. The face of the lower mold 128A to be brought into contact with the conductive foil 110 is flattened. The upper mold 128B has such a shape as to form a cavity above the conductive foil 110 to which the circuit element 122 has been fixed. The mold 128A, 128B has a gate at its side, and resin sealing is performed by filling an insulating resin 120 through this gate.
After performing the molding operation in the aforementioned steps, the backface of the conductive foil 110 is entirely removed up to the part shown by the dotted line of FIG. 13(A), whereby each conductive pattern 121A, 121B and/or 121C is electrically separated. Lastly, a solder resist and an external electrode are formed for backface treatment and are separated into the respective devices by dicing, thus completing a circuit device.
However, in the molding step, there is a situation in which air intervenes between the backface of the conductive foil 110 and the lower mold 128A. Therefore, disadvantageously, air will gather on the opposite side of the gate, and the conductive foil 110 will locally rise in the cavity because of air pressure if the insulating resin 120 is filled through the gate provided at the side face of the mold 128 in this situation. If the conductive foil 110 locally rises within the cavity, the circuit element 122A, 122B and the fine metal wire 125A fixed to the conductive foil 110 in this area will come into contact with the upper mold 128B. Disadvantageously, this causes bending of the fine metal wire 125A or the like.